PIC 16F887 no se puede almacenar los datos de UART en el búfer [cerrado]

ESP8266 y pic 16f887 están conectados en serie con una velocidad de transmisión de 9600. el problema es cuando ESP envía datos a 16f887 y luego el microcontrolador no puede almacenar los datos recibidos en su búfer.

#include <xc.h> 
#include <stdint.h>

__CONFIG(FOSC_HS & WDTE_OFF & PWRTE_OFF & MCLRE_ON & CP_ON & CPD_ON & BOREN_ON & IESO_OFF & FCMEN_ON & LVP_OFF);
__CONFIG(BOR4V_BOR40V & WRT_HALF);

#define _XTAL_FREQ 20000000L


unsigned char MsgFromPIC[] = "\r\nYou typed :";
unsigned char MessageBuffer[64];

int i=0;
void Delay1Second(void);
unsigned char ReadUSART(void);
void putsUSART(unsigned char c);
void ESPWrite(char* st);

void interrupt INTISR(void)
{
    //check if the interrupt is caused by RX pin
    if(PIR1bits.RCIF == 1)
    {
        if(i<64) //our buffer size
        {
            MessageBuffer[i] = ReadUSART(); //read the byte from rx register
            if(MessageBuffer[i] == '\r') //check for return key
            {
                ESPWrite(MessageBuffer);
                for(;i>0;i--)
                    MessageBuffer[i] = 0x00; //clear the array
                i=0; //for sanity
                return;
            }
            i++;
            PIR1bits.RCIF = 0; // clear rx flag
        }
        else
        {
             ESPWrite(MessageBuffer);
             for(;i>0;i--)
                    MessageBuffer[i] = 0x00; //clear the array
             i=0; //for sanity
             return;
        }
    }

}


void main(void) {

    RCIF = 0; //reset RX pin flag

    RCIE = 1; //Enable RX interrupt

    //****Setting I/O pins for UART****//
    TRISC6 = 0; // TX Pin set as output
    TRISC7 = 1; // RX Pin set as input
    //________I/O pins set __________//

    /**Initialize SPBRG register for required 
    baud rate and set BRGH for fast baud_rate**/
    SPBRG = 129;//129@9600;
    BRGH  = 1; 
    //_________End of baud_rate setting_________//

    //****Enable Asynchronous serial port*******//
    SYNC  = 0;    // Asynchronous  
    SPEN  = 1;    // Enable serial port pins
    //_____Asynchronous serial port enabled_______//
    //**Lets prepare for transmission & reception**//
    TXEN  = 1;    // enable transmission
    CREN  = 1;    // enable reception
    //__UART module up and ready for transmission and reception__//

    //**Select 8-bit mode**//  
    TX9   = 0;    // 8-bit reception selected
    RX9   = 0;    // 8-bit reception mode selected
    //__8-bit mode selected__//

    INTCONbits.PEIE = 1;    // peripheral intrrupt enable
    INTCONbits.GIE = 1;     // GLOBL interrupt enable

   // putsUSART('k');

    while(1) //infinite loop
    {

    }

    return;
}

unsigned char ReadUSART(){
    while(!RCIF );

    if(OERR){
        CREN = 0;
        CREN = 1;
    }

    return RCREG;
}
void putsUSART(unsigned char c){
    while(!TXIF);
    TXREG= c;
    //while(!U1STAbits.TRMT);
}
void ESPWrite(char* st){
    char k=0;
    for(; k<i; k++){
        putsUSART(st[k]);
    }
}